1. Field of the Invention
The present invention relates to converting constant volume heating/air conditioning systems to reduce energy consumption.
2. Description of the Related Art
Multizone air conditioning/heating units have been used extensively in buildings and other spaces for occupant comfort, as well as for process temperature and humidity control. Beginning in the late 1940's, these units were widely placed into service.
With multizone units, several different zones (usually from two to twelve or so) were supplied with air from a centrally located air handling unit. The air handling unit typically had both heating and cooling sections, each of which acted on a portion of the circulating air. Based on the temperature sensed in a particular zone, the required air mixture of heated and cooled air was furnished. Mixing of the heated air and the cooled air was accomplished by regulating the amount of air flow through controllable position flow regulating vents. Multizone units were required by their design to transport a constant volume of air continuously during unit operation. That constant volume was designed to meet peak or worst conditions of the hottest and coldest days of the year. Those conditions occurred less than about five percent of the time. The fans in multizone units were required, though, to produce constant volumes of air based on these worst case conditions. Less than peak loads were met by regulating the mixture of heated and cooled air to achieve the desired temperature, based on sensed temperatures in the various zones.
For a considerable time, multizone and double duct constant volume units were almost exclusively the only type installed. The constant volume for production demanded considerable energy usage. This was not considered a problem so long as inexpensive energy was available. However, in the last twenty or so years, energy costs have risen considerably. Removal and replacement of installed multizone units by variable volume units was a possible technique of energy conservation, but this was available only at a considerable cost. As a result, there are a large number of high energy usage, constant air volume multizone heating/air conditioning units still in service.